In 1950, United States along with UK introduced nuclear technology to the then Iran. However relations between Iran and the West degraded following the 1979 Iranian Revolution and the Hostage Crisis that followed. Following this, the US sanctioned Iran.
In 2012 Iran revealed to the world its strong desire of going nuclear and began attemps to enrich Uranium to weapons grade. This led to the Joint Comprehensive Plan of Action or the Iran Nuclear Deal. The deal proposed for Iran to heavily limit its nuclear capacities in exchange for sanction exemptions. However after a change in office in 2016, Donald Trump unilaterally pulled the US out of the Deal in 2017-18. Iran however followed to comply with the deal regardless.
On 5 January 2020, in the aftermath of the Baghdad Airport Airstrike that targeted and killed Iranian general Qassem Soleimani, Iran declared that it would no longer abide by the deal's limitations but would continue to coordinate with the IAEA, leaving open the possibility of resuming compliance. This gets followed up by constantly increasing tensions in the middle east which are a major threat to Iran. In December 2020, Iranian officials expressed further willingness to rejoin the deal, provided that U.S. officials make assurances regarding lifting sanctions and also rejoin.
However Recent reports by the Financial Times have revealed that Iran is once again marching towards weaponisation of its nuclear capabilities as IAEA officers found substantial evidence of the same while a regular inspection of the Iranian Facilities. This has once again catalysed the West, Particularly the E3 (UK, France, Germany) to negotiate a deal with Iran to help prevent nuclear buildup.